ERROR Could not load file or assembly 'AjaxControlToolkit' or one of its dependencies

Question

I'm deploying my website on the server.

My website is done using asp.net c# 4 and EF 4.

I receive this error:

Could not load file or assembly 'AjaxControlToolkit' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.

Any idea how could I fix it?

Answer 1

It looks like you're trying to run it on a version of ASP.NET which is running CLR v2. It's hard to know exactly what's going on without more information about how you've deployed it, what version of IIS you're running etc (and to be frank I wouldn't be very much help at that point anyway, though others would). But basically, check your IIS and ASP.NET set-up, and make sure that everything is running v4. Check your application pool configuration, etc.